Super Mario Winter Wonderland, the true sequel to Super Mario Sunshine
But on a serious note, I hope it has a big overworld like Super Mario 64 while having the great platforming and physics of Galaxy plus it being in HD is always good. Also introduce new enemies and have a different villian than Bowser, he can still be in it tho.
When the herd loses its way, the shepard must kill the bull that leads them astray.